In the core series games

Price

Effect

When held by a Pokémon, it boosts the Pokémon's Special Attack by 50%, but only allows the use of the first move selected. This effect resets when the holder is withdrawn.

Generation IV

In Pokémon Diamond and Pearl, due to a glitch, if a Pokémon uses U-turn and switches into a Pokémon holding Choice Specs that also knows U-turn, that Pokémon will be locked into U-turn. This was fixed in subsequent games.

Generation V to VI

From Generation V onward, if a Pokémon is already locked into a move due to held Choice Specs, if the held Choice Specs is removed while its effect is negated, the Pokémon will be affected by the Choice item lock glitch.

Generation VII

If a Pokémon holding Choice Specs uses a move other than the one it's locked into (such as through Instruct or Dancer), the move will fail and no PP will be deducted.